Smith. — Eyes of Pulmonate Gasteropoda. 



PLATE 4. 



All figures are magnified 833 diameters. 



Figures 37 and 38 are methylen-blue preparations, made by the method of Prentiss. 



Fig. 37. Sensory cell in the accessory retina showing fibrillar network. 



Fig. 38. Shows the course of a few fibrils in a sensory cell as they approach the 



nucleus and form a network. 

 Fig. 39. Vom Rath preparation, showing the cross section of a rod. 

 Fig. 40. Longitudinal section of the neurite-process of sensory cell of accessory 



retina. Vom Rath preparation. 

 Fig. 41. Sensory cell, chief retina; pigment-cell nucleus. Vom Rath. 

 Figures 42 to 45 and 50 are cross sections of sensory cells in the chief retina, show- 

 ing fibrillar network. Betbe preparations. 

 Figs. 42, 43, 45. Sections through the narrow part of the cell. 

 Fig. 44. Section through the nucleus. 

 Fig. 46. Diagrammatic sketch to show the fibrils which stretched across the space 



between mantle and core in a certain vom Rath preparation. 

 Fig. 47. A few neurites from Figure 35, which appear to show fibrillae. Such 



evidence is very rare in methylen-blue preparations. 

 Fig. 48. Portion of a sensory cell from the chief retina, showing neurofibrils. 

 Fig. 49. Terminal portion of a longitudinal section of a rod. Vom Rath 



preparation. 

 Fig. 50. Section of a sensory cell proximal to its nucleus. Compare Figs. 42-45. 

 Fig. 51. Cross sections of two sensory cells of the accessory retina cut at the level 



of the nucleus. Vom Rath preparation. 

 Fig. 52. Portion of a large sensory cell from the accessory retina. Bethe method. 

 Fig. 53. A sensory cell from accessory retina bent on itself so that the very base 



of the rod is seen in cross section and the region (below in the figure) 



between the rod and the proximal part of the cell is sectioned 



longitudinally. 

 Fig. 54. Oblique section of the lower end of a sensory cell from accessory retina, 



showing fibrillae proximal to the nucleus. Vom Rath preparation. 

 Fig. 65. Nearly longitudinal section of a sensory cell, showing the way in which 



the fibrils of the rod finally become transformed into a network in the 



vicinity of the nucleus. 



